Analysis of the positional relationship of the long thoracic nerve considering clinical treatment.

INTRODUCTION: The long thoracic nerve (LTN) has a risk of being damaged during chest surgery and should be considered when performing anesthesia such as a serratus anterior plane block (SAPB). We analyzed the relationship between landmarks-the fourth to ninth intercostal space (ICS) at the midaxillary line (MAL), through which the distal part of the LTN passes-and the LTN. MATERIALS AND METHODS: We used 25 specimens from 17 embalmed Korean cadavers. The MAL, level of rib and ICS, and regions 5 cm anteroposterior to the MAL (aMAL/pMAL) were established to measure the position of the LTN crossing the MAL, pathway of the LTN, and entering points of the LTN to the SA. RESULTS: The LTN crossed the MAL in 76% of the specimens. The LTN crossed the MAL within the fifth to sixth rib level in 70.8%. Seventy-six percent of the branches entered the SA within the fourth to sixth ICS. The fifth rib and ICS were the most frequent regions aMAL; however, several branches were found pMAL. The LTN entered the SA in 92.6% of the specimens within 3 cm anterior and 1 cm posterior to the MAL. CONCLUSIONS: We set the danger zone as 4 cm near the MAL at the fourth to sixth ICS for thoracotomy. In addition, we proposed the fifth ICS in aMAL at the superficial plane as the alternative injection point for SAPB when blocking the LTN, and the fifth ICS in pMAL at the deep plane to prevent blocking the LTN.

Schematic of mean thickness distribution on the lateral aspect of the canine frontal sinus as an experimental model of sinus surgery.

The dog frontal sinus may represent an alternative model dental implant research; its topographical resemblance to the maxillary sinus renders it a potentially favorable experimental environment. The aim of this study was thus to elucidate the anatomical configuration of the canine frontal sinus and histological characteristics, and to determine whether it could be a new canine experimental model for dental implant research. Twenty-four sides of canine frontal bones were harvested. The distance from the nasion to the emerging point of the lateral aspect of the canine frontal sinus was measured with the aid of Lucion software. The thicknesses of the canine frontal sinus wall were measured, and the two specimens stained with hematoxylin and eosin. The mean distance from the nasion to the emerging point of the lateral aspect of the canine frontal sinus was 16.0 mm. The mean thicknesses of the canine frontal bone at 3, 6, 9, 12, and 15 mm lateral to the midsagittal plane were 2.3, 2.7, 3.2, 3.8, and 3.7 mm, respectively. The canine frontal sinus was lined with pseudostratified ciliated columnar epithelium. These data suggest that the canine frontal sinus is a suitable alternative to the canine maxillary sinus as a model for studying various sinus augmentation protocols.

Characterizing the Lateral Border of the Frontalis for Safe and Effective Injection of Botulinum Toxin.

BACKGROUND: The forehead is a common site for injection of botulinum neurotoxin type A (BoNT-A) to treat hyperactive facial muscles. Unexpected side effects of BoNT-A injection may occur because the anatomy of the forehead musculature is not fully characterized. OBJECTIVES: The authors described the lateral border of the frontalis in terms of facial landmarks and reference lines to determine the safest and most effective forehead injection sites for BoNT-A. METHODS: The hemifaces of 49 embalmed adult Korean cadavers were dissected in a morphometric analysis of the frontalis. L2 was defined in terms of FT (the most protruding point of the frontotemporal region), L0 (the line connecting the infraorbital margin with the tragus), and L1 (the line parallel to L0 and passing through FT) such that L2 was positioned 45° from L1 and passed through FT. RESULTS: The distance from FT to the superior margin of the orbicularis oculi was 12.3 ± 3.3 mm. The frontalis extended more than 5 cm along L2 in 49 of 49 cases (100%), more than 6 cm in 47 cases (95.9%), more than 7 cm in 34 cases (69.4%), more than 8 cm in 11 cases (22.4%), and more than 9 cm in 3 cases (6.1%). The lateral border of the frontalis ran parallel to and within 1 cm of the medial side of L2. CONCLUSIONS: Surface anatomy mapping can assist with predicting the lateral border of the frontalis to minimize the side effects and maximize the efficiency of BoNT-A injections into the forehead.

Neurovascular structures of the mandibular angle and condyle: a comprehensive anatomical review.

BACKGROUND: Various surgical interventions including esthetic surgery, salivary gland excision, and open reduction of fracture have been performed in the area around the mandibular angle and condyle. This study aimed to comprehensively review the anatomy of the neurovascular structures on the angle and condyle with recent anatomic and clinical research. METHODS AND RESULTS: We provide detailed information about the branching and distributing patterns of the neurovascular structures at the mandibular angle and condyle, with reported data of measurements and proportions from previous anatomical and clinical research. Our report should serve to help practitioners gain a better understanding of the area in order or reduce potential complications during local procedures. Reckless manipulation during mandibular angle reduction could mutilate arterial branches, not only from the facial artery, but also from the external carotid artery. The transverse facial artery and superficial temporal artery could be damaged during approach and incision in the condylar area. The marginal mandibular branch of the facial nerve can be easily damaged during submandibular gland excision or facial rejuvenation treatment. The main trunk of the facial nerve and its upper and lower distinct divisions have been damaged during parotidectomy, rhytidectomy, and open reductions of condylar fractures. CONCLUSION: By revisiting the information in the present study, surgeons will be able to more accurately prevent procedure-related complications, such as iatrogenic vascular accidents on the mandibular angle and condyle, complete and partial facial palsy, gustatory sweating (Frey syndrome), and traumatic neuroma after parotidectomy.

The Sihler staining study of the infraorbital nerve and its clinical complication.

The infraorbital nerve (ION) is a cardinal cutaneous nerve that provides general sensation to the mid face. Its twigs are vulnerable to iatrogenic damage during medical and dental manipulations. The aims of this study were to elucidate the distribution pattern of the ION and thus help to prevent nerve damage during medical procedures and to enable accurate prognostic evaluation where complications do occur. This was achieved by treating 7 human hemifaces with the Sihler modified staining protocol, which enables clear visualization of the course and distribution of nerves without the accidental displacement of these structures that can occur during classic dissection. The twigs of the ION can be classified into the usual 5 groups: inferior palpebral, innervating the lower eyelid in a fan-shaped area; external and internal nasal, reaching the nosewing and philtrum including the septal area between the nostrils, respectively; as well as medial and lateral superior labial, supplying the superior labial area from the midline to the mouth corner. Of particular note, the superior labial twigs fully innervated the infraorbital triangle formed by the infraorbital foramen, the most lateral point of the nosewing, and the mouth corner. In the superior 3-quarter area, the ION twigs made anastomoses with the buccal branches of the facial nerve, forming an infraorbital nervous plexus. The infraorbital triangle may be considered a dangerous zone with respect to the risk for iatrogenic complications associated with the various medical interventions such as implant placement.

Clinical implications of the middle temporal vein with regard to temporal fossa augmentation.

BACKGROUND: The middle temporal vein (MTV) traverses the temporal fossa between the superficial and deep layers of the deep temporal fascia. During filler injection into a deficient temporal fossa, filling agents may be inadvertently injected into the MTV, which results in vascular complications. OBJECTIVE: To investigate the course of the MTV to enable safe filler injection in the temple area. MATERIALS AND MATERIALS: The course and diameter of the MTV were measured in 18 hemifaces from 9 Korean cadavers. RESULTS: The MTV was located 23.5 and 18.5 mm above the zygomatic arch at the jugale and the zygion, respectively. The diameter of the MTV at its thickest point was 5.1 mm. A splitting and reuniting pattern, such that the MTV occupied more space than a single trunk, was observed in 28% of cases. CONCLUSION: We propose that the safest area for filler injection in temporal fossa augmentation is one finger width above the zygomatic arch.

Description of a novel anatomic venous structure in the nasoglabellar area.

Injectable dermal fillers are frequently used to reduce the appearance of various facial creases and rhytids. However, venous complications can develop while injecting dermal filler, especially in the nasoglabellar area. The aims of this study were to determine the anatomic patterns of the veins in the nasoglabellar area and to elucidate their detailed location with reference to various facial landmarks. Forty-one heads from Korean and Thai cadavers were dissected. When the anastomosing vein between the bilateral angular veins (AVs) was located in the nasoglabellar area, it was designated the intercanthal vein (ICV). The bilateral AVs continued as the facial vein without any communicating branches in 12 cases (29.3%). At the radix of the nose, the AV communicated with the ICV, connecting them bilaterally. The ICV was found above (type IIA) and below (type IIB) the intercanthal line in 26 (63.4%) and 3 (7.3%) cases, respectively. The ICV can be regarded as a candidate causative site for the frequent complications associated with dermal filler injection in the nasoglabellar area, and utmost care should be taken when injecting in this area, such as when performing radix augmentation and softening wrinkles in the glabellar area.

Topography of the greater palatine artery and the palatal vault for various types of periodontal plastic surgery.

The purpose of the present study is to provide useful data that could be applied to various types of periodontal plastic surgery by detailing the topography of the greater palatine artery (GPA), looking in particular at its depth from the palatal masticatory mucosa (PMM) and conducting a morphometric analysis of the palatal vault. Forty-three hemisectioned hard palates from embalmed Korean adult cadavers were used in this study. The morphometry of the palatal vault was analyzed, and then the specimens were decalcified and sectioned. Six parameters were measured using an image-analysis system after performing a standard calibration. In one specimen, the PMM was separated from the hard palate and subjected to a partial Sihler's staining technique, allowing the branching pattern of the GPA to be observed in a new method. The distances between the GPA and the gingival margin, and between the GPA and the cementoenamel junction were greatest at the maxillary second premolar. The shortest vertical distance between the GPA and the PMM decreased gradually as it proceeded anteriorly. The GPA was located deeper in the high-vault group than in the low-vault group. The premolar region should be recommended as the optimal donor site for tissue grafting, and in particular the second premolar region. The maximum size and thickness of tissue that can be harvested from the region were 9.3 mm and 4.0 mm, respectively.

Topography of the lingual foramen using micro-computed tomography for improving safety during implant placement of anterior mandibular region.

The aim of this study was to determine the location and size of the lingual foramina and the course of their canals using micro-computed tomography. Twenty Korean mandibles were scanned using a micro-computed tomography system and reconstructed three-dimensionally to enable observation of the lingual foramina and their canals. Four mandibles (20%) had a single foramen at the lingual side of the mandibular midline, 8 mandibles (40%) had 2 foramina, and 5 mandibles (25%) had 3 foramina. Three mandibles (15%) had 4 small foramina with short canals. The foramina were classified as either superior lingual foramina or inferior lingual foramina according to their vertical location relative to the mental spine. The diameters of superior lingual foramina and inferior lingual foramina were 0.75 ± 0.36 and 0.73 ± 0.38 mm (mean ± SD), respectively. The distances from the inferior border of the mandible to superior lingual foramina and inferior lingual foramina were 12.58 ± 2.49 and 6.43 ± 3.08 mm, respectively. Ten canals (21%) traveled upward to the labial side, 24 canals (51%) downward, and 13 canals (28%) parallel to it. Ten mandibles (50%) had lateral foramina.With regard to implant surgery of the anterior mandibular region, the most hazardous zones for lingual foramina are 0 to 2 mm from the midline, the upper 3 to 17 mm from the inferior border of the mandible, and the anterior 0 to 7 mm from the lingual side. Careful preoperative planning taking into account the anatomical location of these foramina might help to avoid complications due to damage to the foramina, their canals, and their contents.

Realization of masticatory movement by 3-dimensional simulation of the temporomandibular joint and the masticatory muscles.

Masticatory muscles are closely involved in mastication, pronunciation, and swallowing, and it is therefore important to study the specific functions and dynamics of the mandibular and masticatory muscles. However, the shortness of muscle fibers and the diversity of movement directions make it difficult to study and simplify the dynamics of mastication. The purpose of this study was to use 3-dimensional (3D) simulation to observe the functions and movements of each of the masticatory muscles and the mandible while chewing. To simulate the masticatory movement, computed tomographic images were taken from a single Korean volunteer (30-year-old man), and skull image data were reconstructed in 3D (Mimics; Materialise, Leuven, Belgium). The 3D-reconstructed masticatory muscles were then attached to the 3D skull model. The masticatory movements were animated using Maya (Autodesk, San Rafael, CA) based on the mandibular motion path. During unilateral chewing, the mandible was found to move laterally toward the functional side by contracting the contralateral lateral pterygoid and ipsilateral temporalis muscles. During the initial mouth opening, only hinge movement was observed at the temporomandibular joint. During this period, the entire mandible rotated approximately 13 degrees toward the bicondylar horizontal plane. Continued movement of the mandible to full mouth opening occurred simultaneously with sliding and hinge movements, and the mandible rotated approximately 17 degrees toward the center of the mandibular ramus. The described approach can yield data for use in face animation and other simulation systems and for elucidating the functional components related to contraction and relaxation of muscles during mastication.

Topography of the submental artery that should be considered in bleeding during dentoalveolar surgery.

The purpose of the present study was to provide precise data regarding the branching pattern of the submental artery, which should be considered in occasions of bleeding during various dentoalveolar surgical procedures of the mandible, such as implant surgeries, tori removal, and iatrogenic injuries. Twenty-six embalmed adult hemifaces from Korean cadavers were used in this study. The vertical distance, horizontal distance, and diameter of the submental artery were measured from the site of the first premolar to the third molar. In cases where there was penetration of the mylohyoid muscle by the main branches of the submental artery, the same items were measured at that point. The vertical distance between the submental artery and the inferior border of the mandible decreased toward the premolar, whereas the horizontal distance from the lingual plate of the mandible increased gradually as it traveled in the anterior direction. The diameter of the artery narrowed slightly toward the premolar. The main branches of the submental artery perforated the mylohyoid muscle in 14 (54%) of the 26 specimens. As a result of this study, the submental artery is located higher from the inferior border and closer to the lingual plate of the mandible in the region of the molar than that of the premolar. Therefore, clinicians should be more careful of bleeding when performing surgery in the molar region compared with the premolar region. Where the mylohyoid muscle is perforated by the main branches of the submental artery, its point of insertion can be observed in diverse locations.

Microanatomy of the infraorbital canal and its connecting canals in the maxilla using 3-D reconstruction of microcomputed tomographic images.

The current study investigated the anatomy of the infraorbital canal (IOC) and its related small canals in the maxilla. Twenty-eight hemimaxillae from human cadavers were studied. The samples were scanned using microcomputed tomography, and then images were three-dimensionally reconstructed using computer software. The branch point of the canal into the anterior superior alveolar nerve from the IOC occurred at about one third along the length of the IOC in the anterior direction. Just over half of the cases had 1 canal. The branch arose either laterally (21/28) or inferiorly (7/28) from the IOC. There was a canal located at the inferior lateral border of the piriform aperture in all cases. The distribution of the canals in the maxilla is represented indirectly by the course and distribution of the nerve and blood vessels therein. This distribution could explain various phenomena encountered in the clinical field.

Sihler-stain study of buccal nerve distribution and its clinical implications.

OBJECTIVE: The aim of this study was to elucidate the precise distribution of the buccal nerve (BN) and its anatomic relationship with the infraorbital nerve (ION) and mental nerve (MN). STUDY DESIGN: Eight human specimens were subjected to Sihler staining, which is a highly accurate method for visualizing the distribution of nerve fibers without alteration of the nerve. RESULTS: It was found that the BN mainly proceeded medially from its point of entrance near the parotid duct opening to the angular area of mouth, giving off tiny branches along its trajectory. Some of these branches were distributed in upper angular area, over the cheilion, intermingling with branches of the ION. Intermingling of the BN and the MN was also observed in the premolar area of the lower lip. CONCLUSIONS: This new information regarding the distribution of BN should be taken into consideration when evaluating the possible effects of BN damage.

Alveolar regions of the mandible for the installation of immediate-implant fixtures and bone screws of alveolar distractors.

The purposes of this study were to elucidate the anatomic relationship between the dental roots and surrounding tissues and to identify the optimal sites at which to install dental surgical devices including immediate-implant fixtures and alveolar distractors. We made 5 types of measurements on horizontal cross sections obtained at 1-mm intervals from 20 Korean mandibles. The following results were obtained: (1) the mandibular facial plate was thinnest at the canine (0.5-0.7 mm) and became thicker toward the molar region; (2) the thicknesses of the facial and lingual cortical bone in the interdental region increased from anterior to posterior and from coronal to apical aspects; (3) in each section, the buccolingual root was narrower than 4 mm at depths greater than 8 and 9 mm in the central and lateral incisors, respectively, and the maximum mesiodistal root widths were 3.0 and 3.3 mm; (4) the interroot distance increased from anterior to posterior and from coronal to apical aspects; and (5) on the sections of the first and second molars, the diameter of the septal bone ranged from 4.2 to 7.9 mm buccolingually and from 1.3 to 3.3 mm mesiodistally. Achieving successful placements of implant fixtures and bone screws requires an accurate understanding of the anatomic structure at the installation site. The reported anatomic data might facilitate successful treatments and provide crucial information for use when planning and performing placements of dental surgical devices.

Variations in the trabecular bone ratio of the maxilla according to sex, age, and region using micro-computed tomography in Koreans.

These cortical and trabecular bones maintain general bone structure. Bone mineral density (BMD) changes according to increasing age, sex, and teeth loss. From previous studies, the evaluation of BMD changes depended on conventional radiographic analysis. This study investigated the trabecular bone ratio (TBR) in maxillary bone samples based on data obtained by micro-computed tomography and estimated variations in BMD according to age, sex, and tooth loss. Thirty-eight specimens were scanned with micro-computed tomography and reconstructed three-dimensionally. Sections were made parallel to the axis of each tooth, and the TBR was measured. Data were statistically analyzed with 1-way analysis of variance and paired t-tests (α=0.05). The TBR differed significantly (P<0.05) in each tooth region in the dentate group but not in the edentulous group. The mean TBR was higher in men than in women. The TBR reduced more with increasing age in the dentate group than in the edentulous group. The TBR varies according to the presence of teeth, sex, and age in specific teeth regions.

Trabecular bone ratio of mandible using micro-computed tomography in Korean.

Cortical bone and trabecular portion play important roles in maintaining the general structure of bone. It has been reported that a decrease in bone mineral density is related with increasing age, sex, and teeth loss. However, most of the studies were done with conventional radiographic analysis. In addition, data from Korean population are rare. The aim of this study was to analyze trabecular pattern of the mandible using micro-computed tomography. Thirty-nine specimens of the mandible were prepared. Specimens were scanned with micro-computed tomography and reconstructed three-dimensionally. Sections were made parallel to the axis of each tooth. Trabecular bone ratio (TBR) was measured. Data were statistically analyzed with 1-way analysis of variance (alpha = 0.05). There was a statistically significant difference of TBR between dentate and edentulous mandibles in the molar region. Trabecular bone ratio of edentulous mandible in males was greater than that in females. Trabecular bone ratio of dentate mandibles reduced regularly with increasing age, whereas that of edentulous mandibles did not. It could be concluded that there were statistically significant differences in TBR according to presence of tooth, sex, and increasing age on specific areas.

Intramuscular nerve distribution of the masseter muscle as a basis for botulinum toxin injection.

The aim of this study was to determine intramuscular distribution pattern of the masseteric nerve, thus providing information regarding the most efficient and safe site for botulinum toxin (BTX) injection for conventional BTX intervention therapy in the treatment of masseteric hypertrophy.Twelve masseter muscles were dissected, and the pattern of innervation of the masseteric nerve was observed in the superficial, middle, and deep layers. We also analyzed 10 muscles that had been stained using Sihler's staining technique.The nerve branches from the posterosuperior and posteroinferior groups innervating the deep and middle layers of the masseter muscle, respectively. Among the nerve twigs originating from the anteroinferior nerve group, 2 or 3 perforated the superficial layer of the muscle. Observation of stained specimens revealed that all perforating branches innervating the superficial layer were mainly confined to and distributed within areas V or VI.Between 2 and 4 perforating branches supply the superficial layer of the masseter muscle. In addition, the richest arborization of the perforating masseteric nerve branches is confined mostly to area V, approximately in accordance with the BTX injection point that is currently used clinically. Area V is thus strongly recommended as the most efficient and safe BTX injection area for the treatment of masseteric hypertrophy.

Course and distribution of the lingual nerve in the ventral tongue region: anatomical considerations for frenectomy.

The aim of this study was to elucidate the sublingual and intralingual courses of the lingual nerve (LN) in the ventral tongue region, providing a clinical guide for safe surgical procedures such as frenectomy. We evaluated 16 specimens (32 sides) by gross observation after detailed dissections, and a further 6 specimens were examined after Sihler staining. All specimens were harvested from embalmed Korean cadavers. We classified the innervation patterns of the LN into 5 types and confirmed the distribution of the LN in the tip of the tongue. The classification of the LN was made with reference to a line formed by the interlacing of the styloglossus and genioglossus muscles. Based on the course of LN and the presence of a tiny twig (twigs directly innervating the ventral mucosa of the tongue, TM) directly innervating the sublingual mucosa, the course of the LN was classified as being straight, curved, or vertical and with or without the TM. Straight, curved, and vertical courses without the TM were seen in 9.4%, 46.9%, and 18.8% of the cases, respectively. Straight and curved courses with the TM were observed in 6.3% and 18.8% of the cases, respectively. Sihler staining revealed that the tongue tip is innervated by the LN. These findings indicate that surgical manipulations at the ventral tongue region might damage the LN and result in numbness of the tongue tip, and provide a useful anatomic reference for various surgical procedures involving the ventral tongue region.

Clinical implications of the topography of the arteries supplying the medial pterygoid muscle.

The literature contains numerous accounts of the muscular anatomy of the medial pterygoid muscle, but little is known about the detailed vascular supply of the muscle. Numerous surgical procedures, such as mandibular ramus osteotomy, angle reduction, and/or parotidectomy, are performed around the muscle in the absence of this information. This study aimed to clarify the arterial supplies to the medial pterygoid muscle to provide critical information for use during various surgical procedures. Detailed dissections were performed on 20 sides of adult cadaveric head and neck specimens after injecting the carotid artery with red liquid neoprene latex. The medial pterygoid muscle was supplied by the following 5 branches of the external carotid artery: (1) the pterygoid artery of the maxillary artery, (2) a direct muscular branch of the facial artery, (3) the ascending palatine artery, (4) an anterior muscular branch of the facial artery, and (5) a previously undescribed muscular branch of the external carotid artery. This analysis of vascular anatomy has revealed new anatomic information on the blood supplies to the medial pterygoid muscle and will be useful to the development of guidelines for preventing hemorrhage during surgical procedures.